physiology question: Cardiovascular Shock

[omarsaleh66]

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In trying to treat shock, i understand that u can give non-steroidal drugs to stabilize the membrane and to block arachidonic acid.

Why do u want to block arachidonic acid??

i know that it has something to do w prostaglandins and prostaglandins have something to do w blood pressure, but i really dont understand whats the deal??


thanks

Omar

 

[omarsaleh66]

yo

never mind guys, i got my answer.


For those of u who are curious,

prostaglandins,thromboxane, A2, leukotrienes and oxygen radicals are derived from the arachidonic pathway. These all cause an inflammatory response in shock so thats why it was initially thought that blocking the arachidonic pathway could reduce or prevent shock symptoms.



Thanks anyways, im sure alot of u coulda helped me out like u ahve done in the past


Peace

Omar

 

[Kalel]

Well, I think that you are actually referring to septic shock which is a different mechanism then cardiogenic shock. Anyways, in septic shock, it was once thought that NSAIDs may be able to play some role in decreasing the inflammatory response and therefore improving patient outcome; and there were some promising animal studies that suggested this, but no one has ever been able to show any benefit to giving NSAIDS in septic shock. Other anti-inflammatories such as the administration recombinant activated protein C have been able to show improved mortality in septic shock though. I've never heard of any thought being given to giving NSAIDs in cardiogenic shock, except Aspirin of course, which is given for it's anti-platelet and anti-inflammatory effects with the hope of preventing myocardial infarction. It's certainly not a first line agent in cardiogenic shock though, it's not even one of the reccomended therapies. Cardiogenic shock is treated medically by things like inotropes that improve cardiac function and vasodilators that decrease afterload. If you find any papers suggesting that NSAIDs should be used in cardiogenic shock, I'd be intereted in reading them because I had not heard of that.

 

[omarsaleh66]

hey kalel

thanks for clarifying that for me. I kinda understand it better. Indeed i think i had the 2 confused.


peace

Omar

 

[Seaglass]

Activated protein C is only indicated in severe septic shock. Steroids are still commonly given to patients in septic shock due to a believed relative steroid deficiency however the evidence for their use is lacking.

Casey

 

[Mossjoh]

Treating shock depends on identfication of the type of shock first of all...here are a few common types

Cardiogenic shock- The heart is unable to pump blood sufficiently to maintain perfusion of systemic organs and tissues. This often occurs as the result of massive myocardial infarction or arrhythmia. End diastolic pressure is increased. (EDP)

Hypovolemic shock- There is an inadequate blood volume to maintain perfusion and blood pressure. The filling pressures of the heat (EDP) is decreased. This is frequently caused by severe vomiting, diarrhea, and hemmorhage.

Distributive shock- Blood is distributed to the peripheral blood volume and away from the central blood volume by peripheral vasodilation. This is usually caused by sepsis and the release of endotoxin which causes a "cytokine storm" and activation of inflammatory cells, leading to vasodilation and increased vascular permeability.

Obstructive shock- Caused by a process that blocks the filling the heart. A common cause is massive pulmonary embolism, that blocks blood flow through the pulmonary arteries and stops the filling of the left atrium.

Treatment of shock is based upon the underlying cause and also the maintenance of homeostasis. In cardiogenic shock, the cardiac output must be improved. This can be done via adrenergic agonists such as dopamine. Dopamine is convienient because it causes increased cardiac output, and peripheral vasoconstriction at high doses, but dilates renal vascular beds, maintaining renal perfusion and preventing kidney failure.
Hypovolemic shock is treated by giving blood or fluids. If you give fluid, the hematocrit can drop substantially.
Septic shock is treated with antibiotics to treat the underlying infection, and also drugs to counteract the peripheral vasodilation and raise blood pressure and cardiac output. The mortality is still quite high though if the patient is experiencing severe sepsis.

Anyway..I'm blabing, but I hope this helps to explain the various causes and the treatments that would be used in each specific situation. This is by no means complete, but a place to start.

Oh, the prostaglandins can be inhibited to block vasodilation and cause an increase in blood pressure. Careful though not to give these drugs in kidney failure, it will further decrease the GFR.

Mossjoh

 

[Scalpel]

Thanks for the great explanations. I have a related question: why do they give methylprednisolone in spinal shock as part of immediate management. TIA.

 

[jaeida8]

I think methylprednisolone is supposed to decrease neuronal loss.

 

[Seaglass]

RE: Methylprednisone, I believe that this is one of the very controversial conclusions of some spinal trauma studies. The results are definitely not conclusive and is definitely not yet at the level of evidence to be considered standard of care.

Casey

 

[Kalel]

My understanding is that it is given to decrease inflammation and swelling with the hope that it will prevent further irreversible neuronal loss.

 

[Samoa]

Originally posted by cg1155
RE: Methylprednisone, I believe that this is one of the very controversial conclusions of some spinal trauma studies. The results are definitely not conclusive and is definitely not yet at the level of evidence to be considered standard of care.

Casey

Hmm. At every hospital where I've worked so far, it's been the standard of care. I haven't read the original studies, so I don't have an opinion on the quality of evidence, but the Cochrane review supports its use, and that's usually a good barometer. The use of steroids in sepsis is based on a study published in JAMA, and the data supporting its use is actually pretty solid when patients are selected appropriately. But if you're looking for data at the level of all those monster-sized cardiac trials for either of these treatments, then yeah, you're gonna be disappointed.

 

[Kalel]

From emedicine.com:
"The National Acute Spinal Cord Injury Study (NASCIS II) reported significant improvement in motor function and sensation in patients with complete or incomplete SCIs who were treated with high doses of methylprednisolone within 8 hours of injury. "
http://www.emedicine.com/EMERG/topic553.htm
http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&dopt=Abstract&list_uids=86036427
http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&dopt=Abstract&list_uids=90231364

 

[ERMudPhud]

Solumedrol in spinal trauma has pretty much become standard of care based pretty much on the results from one large study(NASCIS II). The Cochrane review was written by the lead author of that study. The study probably had more flaws than it should have for something that has really become standard of care. Their conclusions were based on Post-hoc subgroup analysis-usually a cardinal sin in clinical trials and there has been ongoing fights about the validity of the raw data which has never been released. There is other evidence the steroids complicate the course of spinal injury patients including increased incidence of life threatening infections and longer hospital stays.

Steroids for sepsis has gone back and forth over the years and best evidence I've seen was when a subgroup of septic patients was selected for treatment due to relative adrenal insufficiency based on the results of a ACTH stim test.

 

[Seaglass]

Unless my attendings were trying to screw me over, the general consensus of the 3 programs I have rotated at and the neurology service at my hospital is that the NASCIS trials are severely flawed in design and interpretation and that, although their "conclusions" indicate treatment with steriods, the evidence for their use is questionable at best. So either I guess you believe the trial or you don't, apparently where I've been training they don't. They usually leave the decision up to the attending neurologist.

Asfar as steroids for sepsis, my understanding was only in severly septic patients based on relative deficiency.

As for standard of care, since ERMUDPHUD is currently practicing I'll defer to his position on it, but I doubt if all of my attendings would agree i.e. they would feel that it would be defensible to not give steroids.

Casey